A laminated coil component with a coil conductor included in a component element assembly formed of a magnetic material composition has been heretofore known as an electronic component used for a choke coil that is used at a high-frequency, a power supply circuit through which a large current passes, a power inductor for a DC/DC converter circuit, or the like.
In this type of laminated coil component, when an apparent relative permittivity increases between coil conductors or between a coil conductor and an external electrode to increase a stray capacitance, the resonance frequency may be shifted to a low frequency side, leading to deterioration of high-frequency characteristics.
For avoiding such an increase in stray capacitance, a low-dielectric-constant layer having a low relative permittivity may be provided as a part of the component element assembly.
In this case, however, when different materials are co-sintered in the production process, structural defects such as cracking and peeling may occur due to mutual diffusion and a difference in shrinkage behavior between materials.
Thus, for example, JP 2004-343084 A proposes an electronic component including: a magnetic material part composed of an iron-based oxide magnetic composition; a nonmagnetic material part formed in contact with the magnetic material part and composed of a glass ceramic composite composition; and an internal conductor part formed on at least one of the magnetic material part and the nonmagnetic material part, wherein the glass ceramic composite composition contains a crystallized glass as a main component and a quartz as a filler as a secondary component, the crystallized glass contains 25 wt % to 55 wt % of SiO2, 30 wt % to 55 wt % of MgO, 5 wt % to 30 wt % of Al2O2 and 0 wt % to 30 wt % of B2O2, and the quartz is contained in an amount of 5 to 30 parts by weight based on 100 parts by weight of the crystallized glass and dispersed in the crystallized glass.
In JP 2004-343084 A, the magnetic material part is formed of an iron-based oxide magnetic composition (ferrite-based magnetic material), and the nonmagnetic material part composed of a glass ceramic composite composition is formed in contact with the magnetic material part. A glass ceramic composite composition having reduced mutual diffusion between itself and the iron-based oxide magnetic composition that forms the magnetic material part is used to thereby obtain good co-sinterability.
Since the glass ceramic composite composition described in JP 2004-343084 A has a low magnetic permeability and dielectric constant, good insulation quality, and an effect of suppressing diffusion to a metal material such as Ag, a low-resistance material such as Ag can be used for an internal conductor, so that the direct-current resistance of an electronic component can be reduced.
On the other hand, a metal magnetic material is harder to be magnetically saturated as compared to a ferrite-based magnetic material, and has good direct-current superimposition characteristics, and therefore various kinds of laminated coil components obtained by using the metal magnetic material have been heretofore proposed.
For example, JP 2010-62424 A proposes a method for producing an electronic component, wherein a glass containing SiO2, B2O3 and ZnO as main components and having a softening temperature of 600±50° C. is added to a magnetic alloy material containing Cr, Si and Fe so that the volume of the glass is less than 10% of the volume of the magnetic alloy material, whereby a surface of the magnetic alloy material is covered with the glass to obtain a metal magnetic material, a molded article including a coil is formed using the metal magnetic material, and the molded article is fired at 700° C. or higher and lower than the melting point of a conductor material of the coil in a non-oxidizing atmosphere in vacuum, or without oxygen or at a low oxygen partial pressure.
In JP 2010-62424 A, a sufficient glass film can be formed on the surface of the metal magnetic material, and therefore generation of a gap between metal magnetic materials can be suppressed, whereby the insulation resistance can be increased without increasing the coil resistance, so that an electronic component such as a power inductor, which has good direct-current superimposition characteristics and a low magnetic loss, can be obtained.